The invention discloses a portable vision tester. The portable vision tester comprises an eye lens, a lens disc, a letter disc, a decompression ball and a whistle. The portable vision tester is openedby medical staff, the lens in the lens disc is aligned with a lens barrel through a first motor box; an electric lamp is turned on, and a vision tester observes the letter orientation on the letter disc through the lens; when a vision tester clearly sees the orientation of the letter clearly; the pressure reducing ball which is correspondingly placed upwards is pressed; air in the air bag on thepressure reducing ball is extruded out; extruded air makes the whistle in the decompression ball make a sound. According to the existing vision testing, a visual chart generally is hung on a wall, anddirections of Es in a visual chart are distinguished; however, according to the detection method, an eyesight tester (especially primary and secondary school students) can feel pressure, the test process is interesting, and meanwhile, the light environment can influence the detection result, so that the measured eyesight is inaccurate. The portable vision tester enables the test result to be moreaccurate, is more convenient for medical staff to carry, and enables the detection result to be more accurate.